* Chapter VI 



The Way by which the Blood Passes from 

 the Vena Cava to the Arteries, or from 

 the Right Ventricle of the Heart 

 to the ILeft 



SINCE the close contact of the heart and lungs 

 in man has probably been a source of error, as I 

 have said, the common practice of anatomists, in 

 dogmatizing on the general make-up of the animal 

 body, from the dissections of dead human subjects 

 alone, is objectionable. It is like devising a general 

 system of politics, from the study of a single state, 

 or deigning to know all agriculture from an examina- 

 tion of a single field. It is fallacious to attempt to 

 draw general conclusions from one particular proposi- 

 tion. 



If only anatomists were as familiar with the dis- 

 section of lower animals as with that of the human 

 body, all these perplexing difficulties would, in my 

 opinion, be cleared up. 



The situation is first of all clear enough in fishes, 

 where there is a single ventricle in the heart, and no 

 lungs. The sac at the base of the heart, doubtless 

 corresponding to the auricle, pushes the blood into 



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